This is a prospective, randomized, parallel group study to assess the hemodynamic effect of three different dose regimens of a sustained release (SR) tablet of UT-15C in patients with exercise-induced pulmonary hypertension (PH), as measured by the change in peak total pulmonary resistance index (TPRI) during exercise from Baseline to Week 12.

Prospective, randomized, parallel group study with two periods: a 10 week, dose titration period, followed by a 2 week, dose maintenance period in patients with exercise-induced PH.

The study population will be randomized into Dose Group 1, Dose Group 2, or an Individual Maximum Tolerated Dose (iMTD) of UT-15C SR by Week 10 and maintained through Week 12. Patients may be either currently receiving an approved oral background therapy for their PH (phosphodiesterase-5 [PDE-5] inhibitor, OR endothelin receptor antagonist [ERA]) (no dual background therapy), or not currently receiving therapy for PH.

Inclusion Criteria-

A subject was eligible for inclusion in this study if all of the following criteria applied:

1. Was between the ages of 18 and 75 years of age at Screening

2. Weighed a minimum of 40 kilograms with a body mass index less than 40 kg/m2 at Screening

3. Agreed to have right heart catheterization with exercise performed at Baseline and Week 12, or at the time of early discontinuation of study drug

4. Had exercise-induced PH at Baseline (defined as a PAPm ≥ 30 mmHg during exercise).

   Note: eligible subjects may or may not have had a PAPm ≥ 25 mmHg at rest

5. Exercise-induced PH may have been:

   1. Idiopathic, heritable, drug- or toxin-induced PAH, or PAH associated with connective tissue diseases or HIV infection
   2. Due to ILD
   3. Due to sarcoidosis

6. Had a Baseline pulmonary function tests as follows:

   1. Forced vital capacity (FVC) ≥ 50% (predicted)
   2. If FVC <50% (predicted), total lung capacity (TLC) must be ≥ 50% (predicted)
   3. Forced expiratory volume / forced vital capacity (FEV / FVC) ratio ≥ 50%

7. Had a Baseline 6MWD between 150 and 450 meters, inclusive

8. Was optimally treated with conventional pulmonary hypertension therapy (e.g. oral vasodilators, oxygen, digoxin, etc) with no additions, discontinuations, or dose changes for at least 14 days prior to Baseline (excluding anticoagulants). Oral diuretics may have been adjusted, but not discontinued or added, within 14 days of Baseline

9. May or may not have been receiving an approved PDE-5 inhibitor OR an approved ERA.

   Subjects receiving an approved ERA or an approved PDE-5 inhibitor must have been on a stable dose for 30 days prior to Baseline, and were willing to remain on a PDE-5 inhibitor or an ERA and at the same dose for the duration of the 12-week Treatment Phase. If a subject chose to discontinue their PDE-5 or ERA prior to entering this study, they must have had a ≥30 day washout period between the last dose of the PDE-5 or ERA and start of the screening phase.

10. If female, was physiologically incapable of childbearing or practicing an acceptable method of birth control as deemed appropriate by the physician or institution. Women of childbearing potential had a negative serum pregnancy test at Screening

11. Was able to communicate effectively with study personnel, and considered reliable, willing and likely to be cooperative with protocol requirements, including attending all study visits, in the opinion of the Principal Investigator

12. Voluntarily gave informed consent to participate in the study.

Exclusion Criteria-

A subject was not eligible for inclusion in this study if any of the following criteria applied:

1. Had received epoprostenol, treprostinil, iloprost, beraprost, or any other prostacyclin therapy within 30 days of Baseline (except if used during acute vasoreactivity testing)

2. Had previous intolerance or significant lack of efficacy to an oral or parenteral prostacyclin or prostacyclin analogue that resulted in discontinuation or inability to effectively titrate that therapy

3. Had a concurrent injury, illness (other than PH or a PH related condition), or other confounding factor that would prevent the accurate assessment of the subject's exercise capacity

4. Had a musculoskeletal disorder (e.g. recent hip replacement, artificial leg, etc.) or any other disease that was likely to limit ambulation, or was connected to a machine that was not portable

5. Had portal hypertension

6. Had congenital heart disease (repaired or unrepaired)

7. Had a history or current evidence of left-sided heart disease including myocardial infarction in the previous 3 years or mitral valve stenosis, or evidence of current left-sided heart disease as defined by mean resting pulmonary capillary wedge pressure (PCWPm) or left ventricular end diastolic pressure (LVEDP) > 15 mmHg or left ventricular ejection fraction (LVEF) < 45% (as assessed by either multigated acquisition [MUGA] scan, angiography or echocardiography), or symptomatic coronary artery disease (i.e., demonstrable ischemia either at rest or during exercise)

8. Had acute pulmonary embolism (less than 6 months), chronic thromboembolic disease, pulmonary veno-occlusive disease, or pulmonary capillary hemangiomatosis

9. Had an atrial septostomy

10. Had a current diagnosis of uncontrolled sleep disordered breathing

11. Had PH associated with:

    1. chronic obstructive lung disease (COPD), cystic fibrosis, emphysema, alveolar hypoventilation disorders, chronic exposure to high altitude, developmental abnormalities, schistosomiasis, or chronic hemolytic anemia
    2. hematologic disorders (myeloproliferative disorders, splenectomy)
    3. metabolic disorders (glycogen storage disease, Gaucher disease, thyroid disorders
    4. pulmonary Langerhans cell histiocytosis, lymphangioleiomyomatosis, neurofibromatosis, vasculitis
    5. tumoral obstruction, fibrosing mediastinitis, or extensive loss of lung tissue from surgery or trauma

12. Had chronic renal insufficiency as defined by either a Screening creatinine value greater than 2.5 mg/dL (221 μmol/L) or the requirement for dialysis.

13. Had liver function tests (AST or ALT) greater than three times the upper limit of normal at Screening.

14. Had anemia as defined by a Screening hemoglobin value of less than 10 g/dL, active infection, or any other condition that would interfere with the interpretation of study assessments.

15. Had uncontrolled systemic hypertension as evidenced by systolic blood pressure greater than 160 mmHg or diastolic blood pressure greater than 100 mmHg.

16. Was pregnant or nursing.

17. Had an unstable psychiatric condition or was mentally incapable of understanding the objectives, nature, or consequences of the trial, or had any condition which in the Investigator's opinion would constitute an unacceptable risk to the subject's safety.

18. Was receiving an investigational drug, had an investigational device in place or had participated in an investigational drug or device study within 30 days prior to Screening.